Mark Johnston, senior network design manager, BT Ireland In March 2009, BT Ireland embarked on a major plan to roll out next-generation broadband in Northern Ireland as part of a £2.5 billion UK-wide project (BDUK). A significant investment by BT, including a joint investment partnership with the Department of Enterprise, Trade & Investment (DETI), meant that by March 2012, our next-generation access (NGA) footprint passed 92 per cent of all premises in Northern Ireland. Derry-Londonderry became the only city in the UK or Ireland to have 100 per cent of its street cabinets fibre-enabled. This was achieved by using predominantly very-high-bit-rate digital subscriber line (VDSL) or fibre to the cabinet (FTTC) technology and we are working to drive this percentage even higher under the upcoming DETI Broadband Improvement Project. [login type="readmore"] All of this has been delivered on an open-access basis, whereby any communications provider (CP) can consume the FTTC product at a wholesale level. All of this information is available at an independent website www.nibroadband.com. BT Ireland, therefore, has a strong track record in the delivery of an NGA footprint. However, delivering NGA performance in the final 8-10 per cent of any region is a significant challenge. In getting to 92 per cent coverage, Northern Ireland has seen investment of just short of 2,500 cabinet-based DSLAMs (digital subscriber line access multiplexers) and the fibre infrastructure to support them. DETI’s new Broadband Improvement Project will seek to drive 2Mb broadband as a minimum to all premises in NI and drive additional NGA coverage across the region. Following a recent Open Market Review, where all CPs were asked to provide data on their broadband networks, the output as published by DETI shows there remains approximately 10 per cent of premises in Northern Ireland that cannot get 2Mb broadband. For BT, a significant number of those are already connected to cabinets that have FTTC capability. The reason for this is simply because the line length from the cabinet to the end user is outside the range of VDSL technology. RE-ENGINEERING THE COPPER ACCESS NETWORK Clearly, solving this problem is not a matter of just enabling more cabinets, most of them already have been. My team are currently carrying out a lot of analysis on how and where we could re-engineer the copper access network, as well as taking consideration of alternative technologies such as fibre to the premises (FTTP), wireless to the cabinet (WTTC) and broadband regeneration technology. My team has a close working relationship with our colleagues at Adastral Park in the UK, our global centre of innovation, who lead the R&D effort in developing these alternative technologies. Given the nature of our work and our track record in deploying new technology rapidly into the live environment, their ability to model large-scale networks and the impact of new technologies on network performance is vital in making what ultimately are million-pound investment decisions. Copper re-engineering, as a concept, can sound quite simple. It means looking for opportunities to create new nodes (cabinets) that could then be ‘fibred’ with a new DSLAM. Finding these opportunities is the difficult part. Public switched telephony networks (PSTN) have been built over many years, and the legacy can mean that the relationship between premises and the copper network is not straightforward. At exchange boundaries, or even at cabinet boundaries, houses that geospatially are in close proximity may be fed from entirely different network nodes. Therefore, the range of broadband speeds can vary considerably. Copper re-engineering is the art of looking at how to best augment this relationship. An example of how BT in Northern Ireland is pioneering alternative solutions is our recent pilot of WTTC on Rathlin Island, the northernmost point of Northern Ireland, which will bring NGA to the residents there for the very first time. The typical topology of an NGA network consists of a ‘headend’, which is essentially a Layer 2 switch that drives the Gigabit Passive Optical Network (GPON), and fibre spine cables that deliver the capacity required out to the VDSL muxs in the cabinets. In the case of WTTC, the fibre spine is either partially or entirely wireless, using a hybrid packet transport radio. For Rathlin, this extends the GPON from the shore at Ballycastle on the mainland directly to the cabinet on Rathlin Island. This radio has a fibre presentation, and so the physical integration to the NGA topology is not that complicated. INTEGRATING RADIO INTO SYSTEM STACK What is more difficult, and what the pilot is helping us develop, is the integration of the radio into the existing system stack for the NGA network. The radio is not capable of delivering the same capacity as a fibre optic cable, and the port on the Layer 2 switch is not inherently aware of the presence of the radio or what performance it can sustain at any given time. Taking all of this into consideration, there are limitations on where WTTC will be suitable, but it will still play a valuable part in delivering NGA in challenging rural locations. It is unlikely, however, that copper re-engineering, WTTC and FTTP will deliver a solution to all of the final 8 per cent of premises in Northern Ireland, and so a couple of other tactical solutions are being developed to add to the mixture of tools at our disposal. Broadband regeneration technology is one potential option, extending the reach of asymmetric digital subscriber line from the exchange deeper into the access network – this is not a panacea and there remains a limitation on where in the network it can make a difference. Another option being considered is the role that 4G will play in the delivery of NGA in the future. BT recently acquired its own 4G spectrum, and one potential application for the technology is a bearer for NGA downstream of the cabinet, decoupling the broadband from the legacy copper network. Key also to our NGA growth plan is the Republic of Ireland and we have a keen interest in what is happening in the NGA space here. We have invested significantly in building large broadband networks for our wholesale customers such as Sky and UTV. This includes our nationwide rollout of total transmission (an advanced next-generation mobile backhaul network) and local loop unbundling to offer greater choice for customers in this market. To date, we have 89 telephone exchanges unbundled, with a footprint of over 900,000 lines and we are also pursuing sub-loop (FTTC) unbundling as a way to compete in the NGA space as well. In summary, it is the combination of innovation, experience and the back-up of a global network that makes BT unique in this market, as we continuously seek out new solutions to real communication issues. In the case of Northern Ireland, our approach in taking the rollout of the ‘commercial two-thirds’ and extending it to the ‘final third’ with a subsidy from Government has helped Northern Ireland achieve the position that it is in today, which is ahead of every European country in the rollout and delivery of NGA network infrastructure.